RF receive and transmit non-homogeneity is one of the most effective causes of image non-uniformity in MRI images and is considered as an important source of error in quantitative studies. Part of this non-homogeneity is a characteristic of RF coils and part of it, is due to the interaction of RF field with the body being imaged. In this study, RF field non-homogeneity of a volume head coil is measured in human brain (In vivo) as well as in water and oil phantoms, using a method which was proposed by this group formerly. Comparing the results shows that RF non-homogeneity in water phantom is more than its value in oil phantom. It was also shown that it was even more than its value in human brain In vivo conditions. Non uniformity pattern shows that in both In vivo and water phantom cases, standing wave effect is dominant under our experimental conditions which may cause over-estimating in real magnitudes of Rf non-homogeneity and imaging effective parameters, such that, should has been considered in designing of MRI related phantoms.      

In this research we fabricated different Cu-Ni nanoparticles in order to investigate their catalytical, magnetic and sensitivity of properties. Cu-Ni core–shell nanoparticles on carbon thin films were prepared by co-deposition of RF-sputtering and RF-PECVD. Samples containing Cu nanoparticle were grown on carbon substrate in attendance acetylene and then Ni layers with different thicknesses were grown over these Cu nanoparticles. Topography and atomic structure were investigated by atomic force microscopy (AFM) and X-ray diffraction (XRD), respectively. XRD showed that Cu core nanocrystal and Ni shell nanocrystal were formed on these films. Average particle size of Cu nanoparticles that was estimated by Scherre and Wiliam-son formola were compared. AFM image had a good agreement with William-son results.

Introduction: Liver metastasis is detected in more than one million people in each year. Only 10% of them are eligible for surgery. Radiofrequency ablation is the most popular local ablation technique for the management of the other 90% of the metastases. Complete ablation of the lesion with a safe margin is the goal of such a local ablative method. There is no routine available technique for monitoring the treatment process. MRI is the only method which can monitor tissue ablation in real time however interaction of radiofrequency energy by MRI acquisition makes it impossible for clinical use.Materials and Methods: In our in-vitro study, the effect of bipolar needles was evaluated on the signal intensity of theliver parenchyma. This evaluation was repeated 15 times. A calibration curve was also calculated from the in-vitro measurement of tissue temperature with an interstitial NTC sensor with dedicated data collecting software written by our team. Finally the correlation between temperature and signal intensity was prepared and during the RF ablation, the temperature map could be created in an almost real time manner.Results: Our results show an exponential calibration curve for sensors and a linear reduction of the signal intensities during the RF procedure.Conclusion: We introduce a method for calibration of the MRI signal intensity with tissue temperature between alternative RF pulses. This method brings MR monitoring as the practical method in clinical use. By this innovative technique it is possible for all the hospitals and clinics to use their routine MR scanner for monitoring this ablative technique without any additional hardware.

In this paper a new method for design and realization of a sinusoidal oscillator is ‎proposed. The oscillator has fixed amplitude. As we know the design of this kind of ‎oscillator is very difficult because of its sinusoidal form and fired amplitude. Design ‎is done in state space domain. After designing oscillator is realized base on the ‎concepts of trees and links. In fact we have designed a nonlinear system such that its ‎phase portrait corresponds to oscillation and also prespecified amplitude of the ‎oscillation. Then it is transferred to the time domain. The design of an appropriate ‎nonlinear system is based on the equipotential curves.‎